Looking at the whole oath, I would say it goes with the original á½„Î¼Î½Ï…Î¼Î¹ (or with á½„Î¼Î½Ï…Î¼Î¹ implied), like the future infinitives before it. It seems kind of strange that it would have a series of future infinitives, then a single future indicative, then an infinitive, and then indicatives, but it does make sense.

At first, I also thought it might be an infinitive of purpose but checking the usual grammars there weren't any examples with the future infinitive and I'm not really sure it's possible (or at least common) in this context